Polyvinyl chloride (“PVC”) is a polymer that is commonly used in fields such as construction and commodity packaging. There are two forms of PVC, rigid and flexible. PVC is naturally a rigid polymer, but by adding plasticizer, or combinations of plasticizers, it may advantageously be made more flexible.
Polylactic acid (“PLA”) and polyhydroxy alkanoates (“PHAs”) are additional polymers which are of increasing commercial importance. Advantageously, PLA and PHAs may be derived from renewable biomass resources, rather than from fossil fuels. Moreover, PLA and PHA products are biodegradable. By themselves, however, PLA and PHAs tend to be a rather rigid and brittle polymer. Consequently, it is also advantageous to modify the properties of the biopolymers with a plasticizer.
Plasticizers for such purposes are typically liquids, having relatively low molecular weights. Typical examples of plasticizers include small molecules such as phthalic acid diesters. Such plasticizers are problematic in certain aspects. First, such plasticizers tend to migrate to the surface of the polymer and bloom, where exposure to the polymer may present a health risk. This blooming tendency is believed to be due, at least in part, to the relatively low molecular weight of the plasticizer. In addition, for applications where flexible PVC is to be recycled, the polymeric material can only be reground 2 or 3 times before the plasticizer is broken down enough to lose its properties.
Consequently, it would desirable if a moderate to high molecular weight material could be used as a plasticizer for PVC, PLA and/or PHAs, which would exhibit little to no migration within the polymeric material. It would also be desirable to provide a flexible PVC which could be recycled multiple times before its desired properties are lost.